1. Field of the Invention
The present invention relates to method and apparatus for controlling movement of a cursor on a screen of a display device of a computer system.
2. Description of the Related Art
A computer system is equipped with a display device for inputting and outputting data. A cursor or a mark called icon (hereinafter they are collectively called cursors) is used to indicate a position on the screen of the display device to be processed. In order to move the cursor to a desired coordinate position on the screen, various coordinate pointing devices may be used. A most common one is a cursor control key arranged on a keyboard. A mouse, a joy stick and a track ball can move the cursor in any desired direction on the screen by manipulating an actuator, and the operation thereof is easy and effective.
A mouse usually has a ball bearing on the bottom thereof, and it is rolled on a desk so that coordinates are generated by rotation angles of the ball bearing. A joy stick usually has an actuation rod which is gripped by an operator and inclined in any direction so that coordinates are generated. A track ball has a ball which is rotatable in any direction. The ball is rotated by a palm or finger of an operator so that coordinates are generated by rotation angles of the ball. These devices parallelly produce X-axis movement signals and Y-axis movement signals which determine the direction and distance of movement of the cursor. The computer unit receives the X-axis and Y-axis movement signals and controls the movement of the cursor on the screen in accordance with those signals. The ratio of the movement of the actuator to the movement of the cursor has been predetermined, and the movement of the cursor is controlled in proportion to the movement of the actuator based on the predetermined ratio.
Those technologies are disclosed in JP-A-58-149535, JP-A-58-129643, JP-A-59-111524, JP-A-59-22126, JP-A-57-29941(U), JP-A-59-6240(U) and JP-A-58-90433(U).
The display device has a cursor coordinate memory for storing coordinates of a cursor on a display screen. The cursor is displayed at the stored coordinate position on the display screen. Accordingly, the cursor display position is altered by altering the content of the cursor coordinate memory. The computer unit has a coordinate pointing device, that is, cursor movement actuation means for producing movement command information for the cursor on the display screen, and coordinate update means for sequentially updating the content of the cursor coordinate memory in accordance with the movement command information. Thus, the computer unit sequentially moves the cursor to desired positions on the display screen in accordance with the coordinate information in the cursor coordinate memory.